The present invention relates to a method for burning gaseous, liquid or solid industrial waste, known as special waste, making use of a tubular revolving furnace with a secondary combustion chamber connected in series therewith.
Considerable problems are encountered in disposing of the waste occurring in industry, particularly in the case of toxic, hazardous or pathogenic waste. In the case of the pathogenic waste, covered by the general term "special waste", considerable efforts have to be made now in connection with the disposal of such waste. For much of such waste, disposal is possible by burning in conventional plants. However, special measures must be taken to ensure a constant combustion and, in addition, official requirements and regulations must be satisfied.
In a known plant, use is made of a tubular revolving furnace, the end of which opens into a secondary combustion chamber, where an afterburning of the flue gases received from the furnace takes place. Most of the special waste is burnt out in the revolving tubular furnace. During the burning process, a prerequisite for trouble-free operation is a precise equilibrium of the waste materials, in accordance with the characteristics established prior to burning. However, not only correct temperatures in the tubular revolving furnace are essential for efficient burning, but it is equally important to have sufficiently long residence times. Only then is it possible to achieve an efficient burning of the gases and solids, accompanied by the complete burning of the residual materials.
At the intake-side, water-cooled end wall of the tubular revolving furnace, there are provided filling devices for solid waste, and drums, as well as burners and lances for liquid flammable materials, sludge, polymerizing waste, etc., and also for optional support fuels. Nozzles for the primary combustion air are also provided. The secondary combustion or afterburning chamber following the furnace includes injection devices for liquid waste, particularly aqueous waste without or only with a low calorific value, as well as secondary air nozzles and an additional support burner. Basically all the special refuse is introduced via the intake end wall into the revolving tubular furnace and burnt out, apart from waste water and sewage without or with a low calorific value, which is injected into the afterburning chamber. If such waste water was burnt in the tubular revolving furnace, it would lead to an excessive reduction of the combustion temperature. It is also possible to directly introduce a fermentation gas into the secondary combustion or afterburning chamber, because this gas very rapidly completely burns.
Solids and sludge are fed in via the intake-side end wall to maintain a specific basic loading of the furnace. For automatically controlling the temperature of the revolving tubular furnace use is made of a multicomponent burner, optionally with a lance, enabling gas and also high caloric, liquid waste to be burnt. These materials can be injected individually or in combination with other materials. Said burner is, on the one hand, integrated into the temperature control circuit of the afterburning chamber (the temperature in the tubular revolving chamber and in the afterburning chamber can be set at between 950.degree. and 1300.degree. C.) and, on the other hand, in the control loop, which controls the quantity of steam or hot water of a boiler plant connected downstream of the combustion part of the installation. This burner has its own combustion air supply and is also used as a starting burner.
The main air quantity for combustion in the revolving tubular furnace is called the primary air. The separate introduction of primary air through the end wall of the furnace improves the oxidation conditions, in that the oxidation of the volatile elements also takes place in the solid bed forming in the furnace.
Thus, substances undergo afterburning in the afterburning chamber, which have not yet reacted in the tubular revolving furnace. The unburnt gases and solid particles mainly occur during the combustion process and, in particular, at the end of the revolving tubular furnace, where the residence time is too short in order to completely burn the substances. This afterburning in the afterburning chamber is assisted by the secondary air, which is introduced into the afterburning chamber under high pressure.
Therefore, the flue gases leave the afterburning chamber in a completely burnt-out state and are cooled in the following radiation part of the downstream boiler to approximately 650.degree. C. Following the boiler, the gases pass through a filtering plant, in which most of solid particles are separated from the gas flow.
Known plants of the afore-described type operate reliably and achieve a high number of operating hours every year. However, since essentially all the waste is burnt in the revolving tubular furnace, it must be dimensioned for this quantity and costs are largely determined by the furnace dimensions.